http://www.java.com/en/download/manual.jsp#linUse that link, and grab "Linux (self-extracting file) filesize: 18.83 MB"
http://javadl.sun.com/webapps/download/AutoDL?BundleId=23103 Download it, right click on the downloaded file, select properties/permissions, put check in the box that says "make executable", click "OK"
open terminal, SU and root password.
Execute it by
./jre-6u7-linux-i586.bin
This will install in it's own directory (jre1.6.0_07 currently), so don't worry just follow through the license agreement and all prompts until it says done

Now go into the new jre directory as root, and copy all the contents. They get copied to usr/lib/jaba . Overwrite everything.
you can use "file manager super user" so you can drag and drop, selecting "copy here" then choosing "overwrite all" button.